The disclosed embodiments concern a device for detecting the state of a switch, allowing the closed and/or open state of a switch to be accurately detected. A switch in the disclosed embodiments is an electronic device allowing the passage of a current to be interrupted or allowed. Different types of switches exist, such as mechanically driven switches, electromagnetically driven switches, and relays. The disclosed embodiments apply to any type of switch for which there exists, between the open and the closed state, a measurable difference in the value of an electrical quantity, such as, for example, the voltage at the terminals of the switch, the switch resistance, the current passing through the switch, the power consumed by the switch, etc. Said electrical quantity characterizes the state of the switch.
In the normal state, when an open switch 1 (FIG. 1) is closed (FIG. 2), the voltage U at its terminals is zero (U=0) or practically zero. Therefore when the switch is not used frequently, it happens that it no longer operates properly: as FIG. 3 shows, the switch 1 exhibits at its terminals a non-negligible resistance 2, called RSw in the closed state. The reasons for this are many: humidity, fouled contacts, etc. As FIG. 3 shows, the voltage U at the terminals of the switch is equal to the product of its resistance RSw times the current strength I that crosses it (U=RSwI), according to Ohm's Law.
Consequences follow from this in the reading of information transmitted by the switch. Thus the information relating to the closure of the contact is not transmitted at the time desired or is not even transmitted at all. By way of example, pitch-trim sensors (switches) built into the joystick of a pilot or a co-pilot in an aircraft cockpit allow the aircraft pitch to be restored. In the event of the poor functioning of these sensors, the information stemming from the manipulation of the joystick no longer, or incorrectly, reaches the flight computers and may lead in particular to safety problems.
of the aspects of the disclosed embodiments are directed to accurately detecting the open and/or closed state of the switch in order for the information transmitted by the switch to be reliable and usable by the system receiving said information.